Vladimir Putin has stunned many with his statement that US Secretary of State Clinton is behind the protests in Russia over alleged vote rigging.

Alexei Druzhinin/RIA Novosti/AP

Russian Prime Minister Vladimir Putin speaks at a meeting of the Popular Front in Moscow, Russia, Thursday. Putin blasted US Secretary of State Hillary Clinton for encouraging and supporting the election protesters and warned of a wider Russian crackdown on unrest.

The reason, according to Mr. Putin, that thousands of Russians have taken to the streets? Because Hillary Clinton ordered them to.

Putin, who officially filed his candidacy papers for next March's presidential polls on Wednesday, told supporters that critical remarks made about the transparency and fairness of Russia's Duma elections by the US secretary of State this week were taken as a "signal" by Russian opposition parties.

"She set the tone for some opposition activists, gave them a signal, they heard this signal and started active work," Putin said.

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That claim from the usually level-headed and articulate Putin does not bode well for hopes, expressed by many mainstream Russians in recent days, that the Kremlin will reach out to protesters and take some steps to mollify them, perhaps by seriously investigating some of the more serious allegations of fraud and vote-rigging on behalf of the ruling party, United Russia, rather than by stepping up police measures against them.

"I have no contacts with Hillary Clinton, and get no signals from her whatsoever," says Sergei Mitrokhin, head of the liberal Yabloko party, who was detained by police at an anti-fraud rally on Tuesday evening.

"This looks like an outbreak of hallucinations (at the top)," he says. "But it is a totally inadequate response to fair and reasonable actions of public protest. Our authorities are just displaying their weakness by making claims like this, and they are fast losing credibility with the wider public."

Some 50,000 specially-equipped riot police have been patrolling Moscow streets since the election, and at least 2,000 internal troops have been brought in to help maintain order.

Over 600 people have been detained in Moscow alone in three nights of street protests, and the stage is set for a major confrontation on Saturday when tens of thousands of people are expected to converge on Revolution Square for a rally that authorities say no more than 300 people will be permitted to attend.

Deputy Moscow Mayor Alexander Gorbenko told journalists Thursday that stern police measures will be employed, including 15-day jail terms, if more than 300 people show up on the huge plaza, which is regarded as a sensitive security zone because it abuts the Kremlin. He added that much of the square will be fenced off by Saturday, in order for the Moscow water supply service Mosvodokanal to conduct what he called "emergency repairs."

However, over 40,000 people have already signed an online petition on Russian Facebook, vowing to attend the rally.

"It's not a coincidence that Putin has ditched United Russia, reorganized his campaign and named (popular film director) Stanislav Govorukhin as chief of his election headquarters," says Andrei Piontkovsky, an expert at the official Institute of Systems Analyses in Moscow.

"The thing is, United Russia was caught red-handed in massive manipulations and vote-rigging, and everybody knows it. Putin doesn't want to be chained to that, so he's cutting the party loose," he says.

A coalition of opposition parties claimed Wednesday that as much as 25 percent of the votes cast in Sunday's Duma election may have been falsified. At a Moscow press conference, the group presented the results of a survey of 102 polling stations that suggested United Russia actually won barely a third of the votes, and not the almost 50 percent claimed by the official central electoral commission.

Putin told his supporters Thursday that foreign governments have been funding radical NGO's and opposition groups in an effort to undermine Russian independence.

"Pouring foreign money into electoral processes is particularly unacceptable," said Putin. "Hundreds of millions are being invested in this work. We need to work out forms of protection of our sovereignty, defense against interference from outside.... We have to think of ways to tighten accountability for those who carry out the aims of foreign states to influence domestic political processes."

Some experts say that could portend a tougher crackdown on dissent.

"Since Ukraine's Orange Revolution in 2004, our leaders have been panicking over the threat of colored revolution in Russia, and now that panic is at a fever pitch," says Yury Korguniuk, an expert with InDem, an independent Moscow think thank.

"It's so much easier to scapegoat foreign enemies and their supposed domestic agents than to address society's real discontents, and that appears to be the way Putin is headed," he adds.